Selenated tyrosine and tryptophan analogues have been synthesized for the first time; these substances were shown to be unusually effective mimics for the catalytic action of glutathione peroxidase. A remarkably stable selenotrisulfide was prepared by reaction of t-butyl mercaptan with SeO2. It was established that the oxidation of ketones and aldehydes by SeO2 involves an organoselenium intermediate. The first examples of aza-analogues of SeO2 (i.e., Se(NR)2) were prepared; these substances were found to effect direct allylic amination of olefins. This new allylic amination procedure was used to synthesize gabaculine and is now being applied to the synthesis of the alkaloid acanthione. BIBLIOGRAPHIC REFERENCES: K.B. Sharpless, T. Hori, L.K. Truesdale and C.O. Dietrich, Allylic Amination of Olefins and Acetylenes by Imido Selenium Compounds, J. Amer. Chem. Soc., 98, 269 (1976). K.B. Sharpless and K.M. Gordon, Selenium Dioxide Oxidation of Ketones and Aldehydes. Evidence for the Intermediary of beta-Keto-seleninic Acids, J. Amer. Chem. Soc., 98, 300 (1976).